Transient infrared (IR) thermography is a powerful method of nondestructive testing (NDT) used by the aerospace industry. This short course provides an overview of fundamentals of NDT (TNDT) including cutting-edge test technologies and data-processing algorithms. A review of the properties of a subsurface defect and its host material are presented. Differences of using pulsed and harmonic wave thermal excitation are discussed. TNDT techniques are described and applied by creating defect maps. The course includes demonstrations of two-and three-dimensional thermal models that also illustrate their limits. Examples relate to composite and layered structures used in the aerospace industry, although the same principles apply to most structures. Special attention will be paid to standard and advanced data processing that provides a better reliability of defect detection.